"We looked at five conditions - asthma, diabetes, arthritis, osteoporosis and heart disease," says co-author Professor Laurie Brown of the National Centre for Social and Economic Modelling at the University of Canberra.

The study of more than 7800 adults found that approximately 24 per cent used complementary and alternative medicines (CAMs).

The CAMs included in the study were vitamin or mineral supplements and natural or herbal remedies, including homeopathy.

The highest use of CAMs was by women over the age of 60 years, who had osteoporosis and arthritis.

For example, says Brown, around 40 per cent who had osteoporosis were using CAM products, either on their own or with prescribed medicines.

Aproximately 21 per cent of people with osteoporosis used only CAMs, whereas around 24 per cent used only pharmaceuticals, and 19 per cent used them in combination.

In the case of arthritis, 22 per cent used only CAMs, 22 per cent used only pharmaceuticals and 16 per cent used a combination.

Consult your doctor

Brown says the findings show a significant number of people are using CAMs to treat chronic illnesses, and often in combination with pharmaceuticals.

"If they are using it in combination with prescribed medicines you have to be aware of potential interactions and side-effects," she says.